Lithographic apparatus and device manufacturing method

ABSTRACT

A lithographic apparatus comprising an illumination system for supplying a plurality of beams of radiation, an array of individually controllable elements for imparting to each beam a pattern in its cross section, a substrate table for supporting a substrate, and projection systems for projecting the patterned beams onto the substrate. A displacement system causes relative displacement between the substrate and the projection systems such that the projections beams are scanned across the substrate in a predetermined scanning direction. Each projection system comprises an array of lenses arranged such that each lens in the array directs a respective part of the respective beam towards a respective target area on the substrate. The projection systems are arranged in groups such that lenses in the arrays of different groups direct parts of different beams to different target areas of the substrate that are aligned in the scanning direction. The groups of projection systems are spaced apart in the scanning direction and each group directs beams towards target areas of the substrate that are contiguous and occupy a respective contiguous section of the substrate. Thus different sections of the substrate are exposed by different groups of projection systems, enabling high through put with relatively low substrate displacement speeds and relatively small substrate displacements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 10/994,185, filed Nov. 22, 2004, now U.S. Pat. No. 7,061,581,issued Jun. 13, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lithographic apparatus and a devicemanufacturing method.

2. Related Art

A lithographic apparatus is a machine that applies a desired patternonto a target portion of a substrate. The lithographic apparatus can beused, for example, in the manufacture of integrated circuits (ICs), flatpanel displays, and other devices involving fine structures. In aconventional lithographic apparatus, a patterning means, which isalternatively referred to as a mask or a reticle, can be used togenerate a circuit pattern corresponding to an individual layer of theIC (or other device), and this pattern can be imaged onto a targetportion (e.g., comprising part of one or several dies) on a substrate(e.g., a silicon wafer or glass plate) that has a layer ofradiation-sensitive material (e.g., resist). Instead of a mask, thepatterning means can comprise an array of individually controllableelements that generate the circuit pattern.

In general, a single substrate will contain a network of adjacent targetportions that are successively exposed. Known lithographic apparatusinclude steppers, in which each target portion is irradiated by exposingan entire pattern onto the target portion in one go, and scanners, inwhich each target portion is irradiated by scanning the pattern throughthe beam in a given direction (the “scanning” direction), whilesynchronously scanning the substrate parallel or anti-parallel to thisdirection.

A lithographic apparatus is known in which a pattern is imparted to abeam by an array of individually controllable elements. Rather thanrelying upon a preformed mask (also referred to as a reticle) to imparta pattern to a beam, control signals are delivered to the array ofcontrollable elements to control the state of those elements to patternthe beam. This is generally referred to as “maskless” given that itrelies upon individually controllable elements rather than a mask toimpart the necessary pattern to the beam. A maskless lithographicapparatus can be used to expose relatively large area substrates, forexample substrates to be used as flat panel displays. The panels areexposed in a single pass beneath an array of projection systems, each ofwhich is provided with its own patterning system incorporating an arrayof individually controllable elements. As the substrate is displacedrelative to the projection systems, it is necessary to change the stateof individual elements in the arrays of controllable elements so as tochange the projected patterns. The rate at which the state of theindividual elements can be changed, generally referred to as the updaterate, is limited and this imposes an upper limit on the maximum speed atwhich a substrate can be displaced relative to the projection systems.The speed of displacement determines the maximum throughput of theapparatus, and therefore it is desirable to be able to increase thespeed of displacement.

It is possible to increase the substrate displacement speed byincreasing the number of projection systems devoted to the exposure of asingle track of pixels in the substrate scanning direction. For example,a substrate displacement speed can be doubled if two projection systemsare arranged in series in the scanning direction. With such anarrangement each adjacent pair of pixels in the scanning direction canbe exposed by a respective one of the two projection systems.

The substrate displacement speed can be further improved by addingfurther rows of projection systems. Three rows of projection systemstrebling the maximum speed and four rows quadrupling the maximum speed.Increasing the substrate speed brings with it its own problems howeverin terms of maintaining appropriate speed control and achieving thenecessary acceleration and deceleration of the substrate before andafter scanning of the substrate.

Furthermore, adding extra rows of projection systems increases theoverall distance that a substrate has to be displaced to achieve a fullscan. For example, a row of projection systems capable of exposing thefull width (perpendicular to the scanning direction) of the substrate istypically of the order of 100 millimeters deep in the scanning directionand therefore, given a single row of projection systems and a substrate2 meters long in the scanning direction, a total scan range of 2.1meters is required. Adding a second row of projection systems increasesthe scan range to 2.2 meters and so on.

However, adding additional rows of projection systems does not result ina proportionate increase in throughput. This is because as the totalarea that has to be exposed is also larger, adding one projection systemincreases the total area by the area of that projection system. Inaddition, adding rows of projection systems also increases the physicalfootprint of the apparatus.

Therefore, what is needed is a system and method that increasesthroughput in a maskless lithography system.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is provided alithographic apparatus comprising an illumination system, an array ofindividually controllable elements, projection systems, a displacementsystem. The illumination system supplies a plurality of beams ofradiation. The array of individually controllable elements imparting toeach beam a pattern in its cross section. The projection systemsprojecting the patterned beams onto a substrate. The displacement systemcauses relative displacement between the substrate and the projectionsystems, such that the beams are scanned across the substrate in apredetermined scanning direction. Each projection system comprises anarray of lenses arranged such that each lens in the array directs arespective part of the respective beam towards a respective target areaon the substrate. The projection systems are arranged in groups, suchthat lenses in the arrays of different groups direct parts of differentbeams to different target areas of the substrate that are aligned in thescanning direction. The groups of projection systems are spaced apart inthe scanning direction, such that each group scans beams across arespective area of the substrate as the substrate and projection systemsare displaced relative to each other. The respective areas scanned bybeams from groups that are adjacent to each other in the scanningdirection being contiguous.

According to another embodiment of the present invention, there isprovided a device manufacturing method comprising the following steps.Providing beams of radiation using an illumination system. Using arraysof individually controllable elements to impart to each beam a patternin its cross section. Projecting the patterned beams onto a substrate.Displacing the substrate relative to the patterned beams, such that thebeams are scanned across the substrate in a predetermined scanningdirection. Each beam is directed towards a substrate by a respectivearray of lenses arranged such that each lens in the array directs arespective part of the respective beam towards a respective target areaon the substrate. The projection systems are arranged in groups, suchthat lenses in the arrays of different groups direct parts of differentbeams to different areas of the substrate that are aligned in thescanning direction. The groups are spaced apart in the scanningdirection, such that each group scans beams across areas of thesubstrate as the substrate and projection systems are displaced relativeto each other. The respective areas scanned by beams from groups thatare adjacent to each other in the scanning direction being contiguous.

In one example, it is possible to increase the throughput oflithographic apparatus without increasing the substrate displacementspeed and with a reduction in scan range. This can be achieved becauseessentially contiguous sections of the substrate in the scanningdirection are exposed by different arrays of projection devices.

As discussed above, to expose a two meter long substrate using a singlearray of projection devices that is 1100 mm deep in the scanningdirection would require a scan length of 2.1 meters. Simply adding asecond array of projection devices would increase the scan range to 2.2meters. In contrast, in one example of the present invention a secondrow of projection devices spaced apart with a pitch of one meter enablesthe full two meter length of the substrate to be exposed with a scanrange of as little as 1.05 meters.

In other examples, more than two rows of projection devices can beprovided. For example, three rows of projection devices could beprovided equally spaced apart in the scanning direction. Alternatively,four rows of projection devices could be provided, either equally spacedapart, or in two groups of two rows with the two groups spaced apart inthe scan direction. As a result relatively compact apparatus can achievevery high throughputs without requiring high speed substratedisplacement.

In one example, each group can be arranged to expose a generallyrectangular area of the substrate with the groups spaced apart with apitch of L/N, where L is the length of the substrate to be exposed and Nis the number of groups. Alternatively, each of the contiguous areas canhave a generally rectangular main portion and at least one end portionextending in the scanning direction from the main portion, the endportions of contiguous areas having a saw-toothed shape with the teethof one end section overlapping the teeth of the contiguous end section.The end sections can have a length in the scanning direction equal tothe length in the scanning direction of each group of projectionsystems. With such an arrangement, N groups of projection systems can bedistributed in the scanning direction with a pitch of (L+l)/N, where lis the length in the scanning direction of one group.

In one example, the substrate is displaced relative to stationaryprojection systems. Each lens array can project spots of light that arecapable of exposing tracks on the surface of the substrate, the tracksexposed by one array being contiguous so that the full width(perpendicular to the scanning direction) of the substrate can beexposed in a single pass.

Further embodiments, features, and advantages of the present inventions,as well as the structure and operation of the various embodiments of thepresent invention, are described in detail below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 depicts a lithographic apparatus, according to one embodiment ofthe present invention.

FIGS. 2 and 3 show components of lithographic projection apparatusincorporating arrays of lenses, each of which is arranged to project aspot of radiation onto the substrate, according to various embodimentsof the present invention.

FIGS. 4 and 5 show disposition of spots of radiation projected by a lensarrays, according to various embodiments of the present invention.

FIG. 6 schematically represents an apparatus for exposing a substrate ina single pass of the substrate beneath an array of optical columns eachof which comprises components as illustrated in FIGS. 2 and 3, accordingto one embodiment of the present invention.

FIG. 7 schematically represents the different areas of the substratewhich can be illuminated by each of the optical columns shown in FIG. 6,according to one embodiment of the present invention.

FIG. 8 schematically represents a pattern which it can be desired toexpose on a substrate using the apparatus of FIG. 6, according to oneembodiment of the present invention.

FIG. 9 schematically represents a position of two arrays of opticalcolumns each of the type shown in FIG. 6, according to one embodiment ofthe present invention.

FIG. 10 schematically represents a scan range to expose a full substrateusing the apparatus of FIG. 9, according to one embodiment of thepresent invention.

FIG. 11 schematically represents one embodiment of the present inventionincorporating two groups of optical columns with the groups of opticalcolumns being spaced apart in the scanning direction.

FIG. 12 schematically represents a scan range required to expose a fullsubstrate using the apparatus of FIG. 11, according to one embodiment ofthe present invention.

FIG. 13 schematically represents a scan range required to expose a fullsubstrate using three groups of optical columns that are juxtaposed,according to one embodiment of the present invention.

FIG. 14 schematically represents a scan range required to expose thefull substrate using three groups of optical columns with the threegroups being spaced apart in the scan direction, according to oneembodiment of the present invention.

FIG. 15 schematically represents a scan range required to expose a fullsubstrate using four groups of optical columns, according to oneembodiment of the present invention.

FIG. 16 schematically represents a scan range required to expose a fullsubstrate using an apparatus in which four groups of optical columns areprovided, the four groups being arranged in two pairs spaced apart inthe scan direction, according to one embodiment of the presentinvention.

FIG. 17 illustrates a saw-toothed boundary between areas of a substrateexposed by adjacent projection systems, according to one embodiment ofthe present invention.

FIGS. 18 and 19 illustrate adopting a boundary as illustrated in FIG.17, according to embodiments of the present invention.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers canindicate identical or functionally similar elements.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Overview and Terminology

Although specific reference can be made in this text to the use oflithographic apparatus in the manufacture of integrated circuits (ICs),it should be understood that the lithographic apparatus described hereincan have other applications, such as the manufacture of integratedoptical systems, guidance and detection patterns for magnetic domainmemories, flat panel displays, thin-film magnetic heads, micro and macrofluidic devices, etc. The skilled artisan will appreciate that, in thecontext of such alternative applications, any use of the terms “wafer”or “die” herein can be considered as synonymous with the more generalterms “substrate” or “target portion,” respectively. The substratereferred to herein can be processed, before or after exposure, in forexample a track (e.g., a tool that typically applies a layer of resistto a substrate and develops the exposed resist) or a metrology orinspection tool. Where applicable, the disclosure herein can be appliedto such and other substrate processing tools. Further, the substrate canbe processed more than once, for example in order to create amulti-layer IC, so that the term substrate used herein can also refer toa substrate that already contains multiple processed layers.

The term “array of individually controllable elements” as here employedshould be broadly interpreted as referring to any device that can beused to endow an incoming radiation beam with a patterned cross-section,so that a desired pattern can be created in a target portion of thesubstrate. The terms “light valve” and “Spatial Light Modulator” (SLM)can also be used in this context. Examples of such patterning devicesare discussed below.

A programmable mirror array can comprise a matrix-addressable surfacehaving a viscoelastic control layer and a reflective surface. The basicprinciple behind such an apparatus is that, for example, addressed areasof the reflective surface reflect incident light as diffracted light,whereas unaddressed areas reflect incident light as undiffracted light.Using an appropriate spatial filter, the undiffracted light can befiltered out of the reflected beam, leaving only the diffracted light toreach the substrate. In this manner, the beam becomes patternedaccording to the addressing pattern of the matrix-addressable surface.

It will be appreciated that, as an alternative, the filter can filterout the diffracted light, leaving the undiffracted light to reach thesubstrate. An array of diffractive optical micro electrical mechanicalsystem (MEMS) devices can also be used in a corresponding manner. Eachdiffractive optical MEMS device can include a plurality of reflectiveribbons that can be deformed relative to one another to form a gratingthat reflects incident light as diffracted light.

A further alternative embodiment can include a programmable mirror arrayemploying a matrix arrangement of tiny mirrors, each of which can beindividually tilted about an axis by applying a suitable localizedelectric field, or by employing piezoelectric actuation means. Onceagain, the mirrors are matrix-addressable, such that addressed mirrorswill reflect an incoming radiation beam in a different direction tounaddressed mirrors; in this manner, the reflected beam is patternedaccording to the addressing pattern of the matrix-addressable mirrors.The required matrix addressing can be performed using suitableelectronic means.

In both of the situations described here above, the array ofindividually controllable elements can comprise one or more programmablemirror arrays. More information on mirror arrays as here referred to canbe gleaned, for example, from U.S. Pat. Nos. 5,296,891 and 5,523,193,and PCT patent applications WO 98/38597 and WO 98/33096, which areincorporated herein by reference in their entireties.

A programmable LCD array can also be used. An example of such aconstruction is given in U.S. Pat. No. 5,229,872, which is incorporatedherein by reference in its entirety.

It should be appreciated that where pre-biasing of features, opticalproximity correction features, phase variation techniques and multipleexposure techniques are used, for example, the pattern “displayed” onthe array of individually controllable elements can differ substantiallyfrom the pattern eventually transferred to a layer of or on thesubstrate. Similarly, the pattern eventually generated on the substratecan not correspond to the pattern formed at any one instant on the arrayof individually controllable elements. This can be the case in anarrangement in which the eventual pattern formed on each part of thesubstrate is built up over a given period of time or a given number ofexposures during which the pattern on the array of individuallycontrollable elements and/or the relative position of the substratechanges.

Although specific reference can be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein can haveother applications, such as, for example, the manufacture of DNA chips,MEMS, MOEMS, integrated optical systems, guidance and detection patternsfor magnetic domain memories, flat panel displays, thin film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein can be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein can be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist) or a metrology or inspection tool.Where applicable, the disclosure herein can be applied to such and othersubstrate processing tools. Further, the substrate can be processed morethan once, for example in order to create a multi-layer IC, so that theterm substrate used herein can also refer to a substrate that alreadycontains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of 365, 248, 193, 157 or 126 nm) and extremeultra-violet (EUV) radiation (e.g., having a wavelength in the range of5-20 nm), as well as particle beams, such as ion beams or electronbeams.

The term “projection system” used herein should be broadly interpretedas encompassing various types of projection systems, includingrefractive optical systems, reflective optical systems, and catadioptricoptical systems, as appropriate, for example, for the exposure radiationbeing used, or for other factors such as the use of an immersion fluidor the use of a vacuum. Any use of the term “lens” herein can beconsidered as synonymous with the more general term “projection system.”

The illumination system can also encompass various types of opticalcomponents, including refractive, reflective, and catadioptric opticalcomponents for directing, shaping, or controlling the beam of radiation,and such components can also be referred to below, collectively orsingularly, as a “lens.”

The lithographic apparatus can be of a type having two (e.g., dualstage) or more substrate tables (and/or two or more mask tables). Insuch “multiple stage” machines the additional tables can be used inparallel, or preparatory steps can be carried out on one or more tableswhile one or more other tables are being used for exposure.

The lithographic apparatus can also be of a type wherein the substrateis immersed in a liquid having a relatively high refractive index (e.g.,water), so as to fill a space between the final element of theprojection system and the substrate. Immersion liquids can also beapplied to other spaces in the lithographic apparatus, for example,between the substrate and the first element of the projection system.Immersion techniques are well known in the art for increasing thenumerical aperture of projection systems.

Further, the apparatus can be provided with a fluid processing cell toallow interactions between a fluid and irradiated parts of the substrate(e.g., to selectively attach chemicals to the substrate or toselectively modify the surface structure of the substrate).

Lithographic Projection Apparatus

FIG. 1 schematically depicts a lithographic projection apparatus 100according to an embodiment of the invention. Apparatus 100 includes atleast a radiation system 102, an array of individually controllableelements 104, an object table 106 (e.g., a substrate table), and aprojection system (“lens”) 108.

Radiation system 102 can be used for supplying a beam 110 of radiation(e.g., UV radiation), which in this particular case also comprises aradiation source 112.

An array of individually controllable elements 104 (e.g., a programmablemirror array) can be used for applying a pattern to beam 110. Ingeneral, the position of the array of individually controllable elements104 can be fixed relative to projection system 108. However, in analternative arrangement, an array of individually controllable elements104 can be connected to a positioning device (not shown) for accuratelypositioning it with respect to projection system 108. As here depicted,individually controllable elements 104 are of a reflective type (e.g.,have a reflective array of individually controllable elements).

Object table 106 can be provided with a substrate holder (notspecifically shown) for holding a substrate 114 (e.g., a resist coatedsilicon wafer or glass substrate) and object table 106 can be connectedto a positioning device 116 for accurately positioning substrate 114with respect to projection system 108.

Projection system 108 (e.g., a quartz and/or CaF₂ lens system or acatadioptric system comprising lens elements made from such materials,or a mirror system) can be used for projecting the patterned beamreceived from a beam splitter 118 onto a target portion 120 (e.g., oneor more dies) of substrate 114. Projection system 108 can project animage of the array of individually controllable elements 104 ontosubstrate 114. Alternatively, projection system 108 can project imagesof secondary sources for which the elements of the array of individuallycontrollable elements 104 act as shutters. Projection system 108 canalso comprise a micro lens array (MLA) to form the secondary sources andto project microspots onto substrate 114.

Source 112 (e.g., an excimer laser) can produce a beam of radiation 122.Beam 122 is fed into an illumination system (illuminator) 124, eitherdirectly or after having traversed conditioning device 126, such as abeam expander, for example. Illuminator 124 can comprise an adjustingdevice 128 for setting the outer and/or inner radial extent (commonlyreferred to as σ-outer and σ-inner, respectively) of the intensitydistribution in beam 122. In addition, illuminator 124 will generallyinclude various other components, such as an integrator 130 and acondenser 132. In this way, beam 110 impinging on the array ofindividually controllable elements 104 has a desired uniformity andintensity distribution in its cross section.

It should be noted, with regard to FIG. 1, that source 112 can be withinthe housing of lithographic projection apparatus 100 (as is often thecase when source 112 is a mercury lamp, for example). In alternativeembodiments, source 112 can also be remote from lithographic projectionapparatus 100. In this case, radiation beam 122 would be directed intoapparatus 100 (e.g., with the aid of suitable directing mirrors). Thislatter scenario is often the case when source 112 is an excimer laser.It is to be appreciated that both of these scenarios are contemplatedwithin the scope of the present invention.

Beam 110 subsequently intercepts the array of individually controllableelements 104 after being directed using beam splitter 118. Having beenreflected by the array of individually controllable elements 104, beam110 passes through projection system 108, which focuses beam 110 onto atarget portion 120 of the substrate 114.

With the aid of positioning device 116 (and optionally interferometricmeasuring device 134 on a base plate 136 that receives interferometricbeams 138 via beam splitter 140), substrate table 6 can be movedaccurately, so as to position different target portions 120 in the pathof beam 110. Where used, the positioning device for the array ofindividually controllable elements 104 can be used to accurately correctthe position of the array of individually controllable elements 104 withrespect to the path of beam 110, e.g., during a scan. In general,movement of object table 106 is realized with the aid of a long-strokemodule (course positioning) and a short-stroke module (finepositioning), which are not explicitly depicted in FIG. 1. A similarsystem can also be used to position the array of individuallycontrollable elements 104. It will be appreciated that beam 110 canalternatively/additionally be moveable, while object table 106 and/orthe array of individually controllable elements 104 can have a fixedposition to provide the required relative movement.

In an alternative configuration of the embodiment, substrate table 106can be fixed, with substrate 114 being moveable over substrate table106. Where this is done, substrate table 106 is provided with amultitude of openings on a flat uppermost surface, gas being fed throughthe openings to provide a gas cushion which is capable of supportingsubstrate 114. This is conventionally referred to as an air bearingarrangement. Substrate 114 is moved over substrate table 106 using oneor more actuators (not shown), which are capable of accuratelypositioning substrate 114 with respect to the path of beam 110.Alternatively, substrate 114 can be moved over substrate table 106 byselectively starting and stopping the passage of gas through theopenings.

Although lithography apparatus 100 according to the invention is hereindescribed as being for exposing a resist on a substrate, it will beappreciated that the invention is not limited to this use and apparatus100 can be used to project a patterned beam 110 for use in resistlesslithography.

The depicted apparatus 100 can be used in four preferred modes:

1. Step mode: the entire pattern on the array of individuallycontrollable elements 104 is projected in one go (i.e., a single“flash”) onto a target portion 120. Substrate table 106 is then moved inthe x and/or y directions to a different position for a different targetportion 120 to be irradiated by patterned beam 110.

2. Scan mode: essentially the same as step mode, except that a giventarget portion 120 is not exposed in a single “flash.” Instead, thearray of individually controllable elements 104 is movable in a givendirection (the so-called “scan direction”, e.g., the y direction) with aspeed v, so that patterned beam 110 is caused to scan over the array ofindividually controllable elements 104. Concurrently, substrate table106 is simultaneously moved in the same or opposite direction at a speedV=Mv, in which M is the magnification of projection system 108. In thismanner, a relatively large target portion 120 can be exposed, withouthaving to compromise on resolution.

3. Pulse mode: the array of individually controllable elements 104 iskept essentially stationary and the entire pattern is projected onto atarget portion 120 of substrate 114 using pulsed radiation system 102.Substrate table 106 is moved with an essentially constant speed suchthat patterned beam 110 is caused to scan a line across substrate 106.The pattern on the array of individually controllable elements 104 isupdated as required between pulses of radiation system 102 and thepulses are timed such that successive target portions 120 are exposed atthe required locations on substrate 114. Consequently, patterned beam110 can scan across substrate 114 to expose the complete pattern for astrip of substrate 114. The process is repeated until complete substrate114 has been exposed line by line.

4. Continuous scan mode: essentially the same as pulse mode except thata substantially constant radiation system 102 is used and the pattern onthe array of individually controllable elements 104 is updated aspatterned beam 110 scans across substrate 114 and exposes it.

Combinations and/or variations on the above described modes of use orentirely different modes of use can also be employed.

FIGS. 2 and 3 show components of lithographic projection apparatusincorporating arrays of lenses, each of which is arranged to project aspot of radiation onto the substrate, according to various embodimentsof the present invention.

Referring now to FIG. 2, the apparatus shown comprises a contrast device1, an underside surface of which supports a two dimensional array ofelements 2. Each element 2 in the array can be selectively controlled toact either as an absorber or reflector of radiation. A beam splitter 3is positioned beneath contrast device 1. An illumination source 4directs a beam of radiation 5 towards beam splitter 3. Beam of radiation5 is reflected onto the lower surface of contrast device 1. One ofelements 2 of contrast device 1 is shown as reflecting a component partof beam 5 back through beam splitter 3 and projection optics defined bylenses 6, 7, and 8. A lowermost lens 8 is a field lens that produces asubstantially telecentric beam, which is directed towards a microlensarray 9. Microlens array 9 comprises a two dimensional array of smalllenses each of which is arranged so as to focus light incident upon itonto an upper surface of a substrate 10. Thus, for each of elements 2 incontrast device 1 that acts as a mirror, a respective one of the lensesin microlens array 9 is illuminated, and a respective spot of light isprojected by that lens in microlens array 9 onto the upper surface ofsubstrate 10.

Referring to FIG. 3, this is an alternative representation of componentsshow in FIG. 2. In FIG. 3, substrate 10 is shown supported on asubstrate table 11 beneath microlens array 9. Projection optics arerepresented by a simple rectangle 12. Three contrast elements 2 ofcontrast device 1 of FIG. 2 are shown above projection optics 12. Inthis embodiment, substrate table 11 is moved in a linear manner in adirection of arrow 13 beneath microlens array 9. In an alternativearrangement, substrate 10 can be moved in a linear manner on astationary table 11.

FIGS. 4 and 5 show disposition of spots of radiation projected by a lensarrays, according to various embodiments of the present invention.

Referring to FIG. 4, this drawing is illustrative of the relationshipbetween the disposition of individual lenses in microlens array 9 ofFIGS. 2 and 3 and a direction of displacement of substrate table 11 ofFIG. 3. Again, the direction of displacement is represented in FIG. 4 byarrow 13. That direction is parallel to a line 14 which is inclined to afurther line 15, which extends parallel to a row of the lenses inmicrolens array 9. Each lens projects light onto a different one of arectangular array of spots one of which is identified by numeral 16. Thelenses are arranged in a regular two dimensional array that is slightlyinclined to direction 13 of substrate table movement, as shown such thatthe entire surface of substrate 10 can be exposed by appropriate controlof the illumination beams delivered to the respective lenses by therespective elements 2 of contrast device 1. Each lens can in effect“write” a continuous line on the surface of substrate 10 and, given thedisposition of the lenses relative to the direction of substratemovement, those lines are sufficiently close together to overlap.

In one example, to expose a selected two dimensional area of substrate10, substrate 10 is advanced beneath microlens array 9 and theindividual lenses beneath which the area to be exposed is positioned atany one time are illuminated by rendering the associated elements 2 ofcontrast device 1 reflective.

In FIG. 4, the continuous lines that can be written by individual lensesof microlens array 9 overlap to a significant extent in the directionperpendicular to the scan direction represented by arrow 13. In oneexample, such overlap is not necessary, and the full surface area of asubstrate could be exposed using an arrangement in which projected spotsthat are adjacent in the direction perpendicular to the scan directionjust touch, but do not overlap. Such an arrangement, which minimizes thetotal number of spots required to expose a given area, is desirablewhen, as is often the case, the production rate is limited by the rateat which the intensity of individual spots 16 can be changed.

In one example, individual spots are generally circular, but when usedto expose pixels that are square some overlap between adjacent spots isrequired. With reference now to FIG. 5, a disposition of four spots 17,18, 19 and 20 are arranged so that the continuous lines that can bewritten by each of the spots just touch, but do not overlap. Spots 17-20have a pitch P and a diameter d. The scan direction is represented bythe lines between which the four spots 17-20 are located. Thus spots 17and 20 are projected by adjacent lenses in a row of lenses extendingtransverse to the scan direction, whereas the spots 17 and 18 areprojected by adjacent lenses 8 in a column of lenses of microlens array9. The column is inclined by a small angle to the scan direction. Spots17 and 20 are separated by a distance equal to six times the diameter dof each spot. Thus, in order to fully expose substrate 10, each columnof microlens array 9 has seven lenses.

It is to be appreciated that FIG. 5 is schematic, and is notrepresentative of the scale of an actual apparatus. For example,microlens array 9 would typically have a lens pitch P of the order ofabout 150 micrometers, with each of the lenses projecting a spot (forexample spot 17) with a diameter d equal to about 1.25 microns. The spotdiameter d would typically be greater than the pixel track width toprovide limited overlap between adjacent tracks, but for the purposes ofillustration it is assumed that the spot diameter d is equal to thepixel track width. Assuming such dimensions apply, microlens array 9 has120 rows of lenses spaced apart in the scan direction so as to ensurecoverage of the full width of substrate 10 between spots that areadjacent in a common row extending transverse to the scan direction (forexample spots 17 and 20 in FIG. 5).

In one example, to achieve appropriate resolution (spot size) atsubstrate 10, an appropriate numerical aperture is used. For example,this can be about 0.15. If the spacing between microlens array 9 (seeFIG. 3) and substrate 10 is about 500 micrometers, the pitch P of thelenses in microlens array 9 will be at least about 150 micrometers. If afree working distance is, for example, about 1000 micrometers, the lenspitch P has to be greater, for example about 300 micrometers. A pitch Pof 150 micrometers requires 120 lenses assuming a spot diameter d ofabout 1.25 micrometers at substrate 10. An array of lenses with adimension of about 18000 micrometers in the scan direction (120×150).With a pitch P of about 300 micrometers, 240 rows of lenses extendingtransverse to the scan direction are used to fully cover the about 300micrometer gap between adjacent lenses in each row. Thus, the number ofrows of lenses is doubled as is their spacing, and therefore the lengthin the scan direction of micolens array 9 is quadrupled to about 720,00micrometers (300×240).

If all the lenses in microlens array 9 were arranged in a single rowextending transverse to the scan direction, exposure of the full lengthof substrate 10 would require transport of substrate 10 by that fulllength plus a very small distance corresponding to the scan-directiondimension of the row of spots. Given the number of rows of lensesrequired to expose the full width of substrate 10, the minimum scandirection is a function of the dimension in the scan direction ofmicrolens array 9.

In addition, although the “footprint” of an individual array of lensesis relatively limited (for example 18,000 micrometers in the case of afree working distance of 500 micrometers, a pitch of 150 micrometers,and a spot diameter of 1.25 micrometers), in practice the footprint ofan optical column, of which a lens array forms part, is larger than thefootprint of the array itself given the presence of lenses and othercomponents above the lens array itself, for example the components 6, 7and 8 in FIG. 2.

FIG. 6 schematically represents an apparatus for exposing a substrate ina single pass of the substrate beneath an array of optical columns eachof which comprises components as illustrated in FIGS. 2 and 3, accordingto one embodiment of the present invention. This embodiment illustratean additional demand for space. A substrate 22 is displaced across asubstrate table 21 in the direction indicated by arrow 23 beneath anarray 24 of six optical columns 25. Each optical column 25 isillustrated as having a circular periphery representing the overallfootprint of that column 25, within which there is an area 26 that isshaded that corresponds to an actual optical footprint of that column 25upon substrate 22 as it is advanced beneath that column 25. It is to beappreciated that, although for the purposes of illustration only sixoptical columns 25 are shown in FIG. 6, in practice it can be the casethat there are, for example, twenty five optical columns 25 arrangedacross the table 21.

FIG. 7 schematically represents the different areas of the substratewhich can be illuminated by each of the optical columns shown in FIG. 6,according to one embodiment of the present invention. The opticalfootprints of the optical columns 25 are contiguous, such that the sixoptical columns 25 together can expose the full width of substrate 22.Broken lines represent the boundaries between the optical footprints ofadjacent columns 25. Thus, each optical column 25 exposes a respectivetrack 27 extending between a respective pair of broken lines 28, thetracks 27 covering the full width of substrate 22 between boundariesrepresented by full lines adjacent side edges 29 of substrate 22.

Within each track 27 the surface of substrate 22 can be considered asbeing made up of a series of pixels, each of which may or may not beexposed during scanning of substrate 22.

FIG. 8 schematically represents a pattern that can be desired to exposeon a substrate using the apparatus of FIG. 6, according to oneembodiment of the present invention. A row 30 of pixels are shown withalternate pixels shaded. Each row 30 of pixels corresponds to a tracktraversed by a single lens of one of optical columns 25. For example,pixel 31 is to be fully exposed (“white”), pixel 32 receives noradiation (“black”), and pixel 33 is fully exposed (“white”). Afrequency at which the individually controllable contrast elements 2(FIGS. 2 and 3) can change their state determines a rate at which thepatterned beam projected onto substrate 22 can be changed. This sets alimit on a speed at which substrate 22 can be transported past opticalcolumn 25. If substrate 22 is traveling too fast, the contrast elements2 cannot switch states sufficiently quickly to deliver the appropriateexposure to individual pixels. For example, assuming an update of 50kilohertz (the number of times that the state of an individual contrastelement 2 can be switched per second), and a pixel dimension of about1.25 micrometers, then the maximum speed at which substrate 22 can bedisplaced is about 62,500 micrometers per second. This assumes that eachpixel is exposed for a duration which is very short as compared with thespeed at which substrate 22 is being transported, such that eachexposure is delivered to a given pixel over a period during whichsubstrate 22 is not displaced significantly.

In another example, when the contrast device 1 can only be updated atabout 25 kilohertz, individual contrast devices cannot be updatedsufficiently quickly to change their state as between adjacent pixels ina particular pixel track 30, and therefore one optical engine can onlyexpose alternate pixels in a particular track 30. Therefore, either thescanning speed of substrate 22 has to be reduced to only about 31,250micrometers per second or alternative arrangements must be made.

FIG. 9 schematically represents the position of two arrays of opticalcolumns 25 each of the type shown in FIG. 6, according to one embodimentof the present invention. In this embodiment two arrays 24 of opticalcolumns 25 each substantially identical to single array 24 shown in FIG.6. Each array 24 is allocated to the exposure of alternate rows ofpixels, such that for example in FIG. 8 one array would be responsiblefor the exposure of pixels 31 and 33, while the other array would beresponsible for exposure of pixel 32 and the two pixels, other thanpixel 32 which are adjacent to pixels 31 and 33. In this embodiment, atotal scan range required to expose the full surface of substrate 22 isincreased by a length in the substrate scanning direction of one of theoptical column arrays 24.

In one example, a free working distance of about 500 micrometers and apitch of about 150 micrometers, a microlens array dimension in thedirection of scanning will be about 18,000 micrometers. In this example,to accommodate optical components other than the microlens array 9,adjacent optical columns 25 have to be offset in the scanning directionas represented in FIGS. 6 and 9. As a result, each optical column 25 canoccupy a relatively large distance in the scanning direction, forexample, about 100,000 micrometers. Thus, with the arrangement shown inFIG. 6, and substrate 22 with a dimension in the scanning direction ofabout 2 meters, the total scan range required to expose the fullsubstrate will be about 2.1 meters. With the arrangement shown in FIG.9, the total scan range will be 2.2 meters. Thus with each additionaloptical column array 24 an additional 0.1 meters is added to the scanrange.

In this embodiment, an increase in the size of the substrate table andthe overall footprint of the apparatus can result. With increasing sizecomes increasing cost and difficulty with regard to maintaining stableprocess conditions across the scan range. In some circumstances, it canbe impossible to upgrade an existing apparatus to accommodate anincreased scanning range simply by adding extra arrays of opticalcolumns.

FIG. 10 schematically represents a scan range to expose a full substrate34 using the apparatus of FIG. 9, according to one embodiment of thepresent invention. This embodiment shows the effect of adding an extraarray of optical engines 36,37 to increase the required scan range. Inthis embodiment, substrate 34 has a length L as represented by arrow 35and two arrays of optical columns 36 and 37 are provided, each with alength l represented by arrows 38 and 39. Substrate 34 has to be movedfrom the position shown in the upper half of FIG. 10 to the positionshown in the lower half of FIG. 10. The total displacement is thereforeL+2l. If substrate 34 only had to move beneath a single array of opticalcolumns, for example array 36, the distance that substrate 34 would haveto be displaced would be L+l. Thus, in order to double the speed atwhich substrate 34 can be displaced, it is necessary to increase thescan range from L+l to L+2l. Therefore, the throughput is not doubled bydoubling the number of optical columns and doubling the speed ofdisplacement of substrate 34.

FIG. 11 schematically represents one embodiment of the present inventionincorporating two groups of optical columns 36, 37 with the groups ofoptical columns 36, 37 being spaced apart in a scanning direction. Thetwo arrays of optical columns 36 and 37 are provided to expose substrate34, each of the columns 36 and 37 exposing a respective generallyrectangular area of substrate 34 with the two generally rectangularareas being contiguous.

FIG. 12 represents a total scan range that substrate 34 has to move inorder to expose the whole substrate, according to one embodiment of thepresent invention. Again, arrow 35 represents the length L of thesubstrate 34 and arrows 38 and 39 represents lengths, in the scandirection, of the arrays of optical columns 36 and 37. The upper half ofFIG. 12 shows substrate 34 at the beginning of a scan, and the lowerhalf of FIG. 12 shows substrate 34 at the end of the scan. It is to beappreciated that, in order for each of the generally rectangular areasof the substrate 34 to move beneath one of the arrays of optical columns36, 37, substrate 34 is be displaced by a distance represented by arrow40, that is by a distance equal to (L+2l)/2. Thus, as compared with thearrangement of FIG. 9, the speed of substrate displacement is halved, asis the displacement distance.

In one example, given an update rate for the pattern imparting contrastdevices of about 12.5 kilohertz, a pixel size of about 1.25 microns, asubstrate with about a 1 meter length in the scan direction, and anoptical column array with a length in the scan direction of about100,000 microns, then the maximum speed at which a substrate can bemoved past the structure shown in FIG. 9 would be(1,000,000+100,000)/(1.25×12500)=about 70.4 seconds. If a second row ofoptical columns is added as shown in FIG. 9, the time taken to scan thesubstrate will be (1,000,000+200,000)/(2×1.25×12500)=about 38.4 seconds.

To achieve a full scan in 38.4 seconds, the velocity of the substrateassuming a constant speed over the full exposure process will be 0.03125meters per second.

In contrast, with two arrays of optical columns 36, 37 arranged as shownin FIG. 11, the time taken to expose the full substrate will be(500,000+100,000)/1.25×12500 which equals about 38.4 seconds. Thus, thetime taken for a single scan is exactly the same as in the case of FIG.9. However, the total displacement of substrate 34 during the scanningprocess is halved, as is the substrate velocity.

FIG. 13 schematically represents a scan range required to expose a fullsubstrate using three groups of optical columns that are juxtaposed,according to one embodiment of the present invention. Three arrays ofoptical columns 41,42 and 43 arranged to expose a substrate 44, adimension 45 indicating the total scan range.

FIG. 14 schematically represents the scan range required to expose afull substrate using three groups of optical columns with the threegroups being spaced apart in a scan direction, according to oneembodiment of the present invention.

In FIG. 13, optical column array 41 exposes every third pixel along thelength of substrate 44, while in FIG. 14 optical column 41 exposes eachpixel of a generally rectangular area occupying a left hand third ofsubstrate 44. Thus, for an identical scan duration in FIG. 14, thesubstrate scan speed and substrate displacement are reduced by a factorof three as compared with FIG. 13.

In the examples of the invention represented in FIGS. 12 and 14,individual arrays of optical columns are equally spaced apart along thelength of the scan range with a pitch equal to L/N, where L is thelength of the substrate to be exposed and N is the number of groups ofoptical columns. It is possible, however, to have groups of arrays ofoptical columns arranged along the direction of scan.

FIG. 15 schematically represents a scan range required to expose a fullsubstrate using four groups of optical columns, according to oneembodiment of the present invention. In this embodiment, the fouroptical column arrays arranged adjacent each other so as to be able toscan a substrate 50. An upper half of FIG. 15 shows substrate 50 as itsleading edge just reaches an optical column array 46, and a lower halfshows a trailing edge of substrate 50 as it just leaves the trailing endof an optical column array 49.

FIG. 16 schematically represents a scan range required to expose a fullsubstrate using an apparatus in which four groups of optical columns areprovided, the four groups being arranged in two pairs spaced apart inthe scan direction, according to one embodiment of the presentinvention. This in contrast to FIG. 15, in FIG. 16, equivalent opticalcolumn arrays 46, 47, 48 and 49 are arranged in two pairs, a upper halfof FIG. 16 showing substrate 50 just before the beginning of a scan, anda lower half of FIG. 16 showing substrate 50 immediately after the scan.

Whereas in FIG. 16 the scan range as represented by arrow 51 is equal tothe overall length in the scan direction of substrate 50 plus four timesthe length in the scan direction of each of the optical column arrays,in FIG. 16 the scan range is indicated by arrow 52 and is equal to halfthe length of the scan range 51 in FIG. 15. Once again, for a giventhroughput, the scan range and speed is halved in the case illustratedin FIG. 16 as compared with the case illustrated in FIG. 15.

FIGS. 12, 14 and 16 assume that each of the spaced-apart groups ofoptical columns exposes a respective one of a series of contiguousgenerally rectangular areas on the substrate, the contiguous areashaving mutual boundaries defined by straight lines extending parallel tothe leading and trailing edges of the lens arrays such as the lens arrayshown in FIG. 4. With such an arrangement, each of the generallyrectangular areas is displaced relative to the optical columns by adistance equal to the length of the rectangle in the scan direction plusthe width of the optical column group in the scan direction. Analternative approach is possible in which the boundaries betweenadjacent contiguous areas to be exposed by adjacent groups of opticalcolumns have a saw-tooth shape. This is possible because of thedistribution of lenses in the optical columns, as schematicallyrepresented in FIG. 4, and as further described below with reference toFIG. 17.

FIG. 17 illustrates a saw-toothed boundary between areas of a substrateexposed by adjacent projection systems, according to one embodiment ofthe present invention. Assuming that a portion of substrate is beingtransported in the direction of arrow 53 beneath an array of lenses,such as schematically represented in FIG. 4, but having many more lensesthan are depicted in FIG. 4, then line 54 represents the track of thelens at the top left hand corner of the array and line 55 represents thetrack of the lens at the bottom right hand corner of the array. Line 56represents the position in the scan direction of the bottom left handlens of the array, and line 57 represents the position in the scandirection of the top right hand lens of the array. The shaded area 55represents an area of the substrate that is exposed by one group ofoptical columns, and the unshaded area 59 represents an area of thesubstrate that is exposed by the adjacent group of optical columns. Theboundary between these two areas is saw-tooth shaped. Thus, the areasexposed by adjacent groups of optical columns overlap in the scandirection, with each area having a main generally rectangular area andan end portion with a saw-tooth edge, the end section having a length inthe scanning direction equal to the length in the scanning direction ofeach group of projection systems.

FIGS. 18 and 19 illustrate adopting a boundary as illustrated in FIG.17, according to embodiments of the present invention. This can resultin desired number of groups of optical columns required to achieve aparticular throughput.

FIG. 18 corresponds to FIGS. 11 and 12, in which two groups of opticalcolumns are used to expose respective generally rectangular areas of thesubstrate. In FIG. 18, optical column group 60 is used to exposegenerally rectangular shaded area 61 extending from the left hand sideof the group 60, and optical column group 62 is used to expose generallyrectangular shaded area 63 extending from the left hand side of group 60to the left hand side of group 62.

FIG. 19 represents the case as explained with reference to FIG. 17, inwhich a section of the substrate extending in the scan direction isexposed by both of optical column groups 60 and 62. Optical column group60 is used to expose part of the substrate areas 64 beneath group 60 andsubstrate areas 65 extending to the left of group 60. Optical columngroup 62 is used to expose part of substrate are 64 beneath group 60 andsubstrate area 66 extending to the right of group 60.

In the case illustrated in FIG. 18, in some circumstances the number ofoptical column groups required to achieve a given throughput can begreater than the number required in the case illustrated in FIG. 19.This difference is explained further below.

If there is only one group of optical columns, as in the caseillustrated for example in FIG. 10, the number of optical columnsrequired in the scan direction can be expressed as follows:$N_{oc} = \frac{L_{s} + L_{ocg}}{L_{p} \cdot f \cdot {ET}}$

where:

-   -   N_(oc)=number of optical columns    -   L_(s)=length of the substrate in the scan direction    -   L_(ocg)=length of the optical column group in the scan direction    -   L_(p)=length of each pixel to be exposed in the scan direction    -   f=maximum frequency at which individual pixels can be addressed    -   ET=the throughput, that is the time within which a full        substrate has to be exposed.        L _(ocg) =N _(oc) .L _(oc)

where L_(oc) is the length of one optical column in the scan direction,and therefore:$N_{oc} = \frac{L_{s}}{{L_{p} \cdot f \cdot {ET}} - L_{oc}}$

N_(oc) is an integer. Assuming a throughput time ET of about 29 seconds,an addressing frequency of about 10 kHz, a substrate length Ls of aboutIm, and optical column length L_(oc) of about 0.1 m, and a pixel lengthL_(p) of about 1 μm, then to achieve the target throughput requiresabout 5.26 optical columns, which in practice requires six opticalcolumns.

Separating the optical columns as depicted in FIG. 18 into two groups ofthree would result in a substrate length to be exposed by each group ofL_(s)=0.5. Thus, each group would require about 2.63 optical columns(half 5.26), that is in practice three optical columns. Thus, for thegiven throughput, there would still be a need for a total of six opticalcolumns.

In the case as illustrated in FIG. 19, in which a section of thesubstrate is exposed by both of the two groups of optical columns, theequation determining the number of optical columns required to achieve agiven throughput is different from that above as follows:$N_{oc} = \frac{L_{s} + {L_{ocg}/N}}{L_{p} \cdot f \cdot {ET}}$

where N=number of groups of optical engines. The above equation can besimplified to:$N_{oc} = \frac{L_{s}}{{L_{p} \cdot f \cdot {ET}} - {L_{oc}/N}}$

If two groups of optical engines are provided, then:N_(oc)=4.17

Thus each group would require about 2.09 optical columns, which issubstantially less than the 2.63 required with an arrangement, such asthat illustrated in FIG. 18, but still would, in practice, require threeoptical columns per group. If, however, the optical columns werearranged in four groups, the above equation indicates:N_(oc)=3.77

Thus, given four optical columns equally spaced apart in the scandirection with adjacent columns exposing overlapping areas of thesubstrate, a throughput can be achieved which requires six opticalcolumns, if the optical columns are all arranged in a single group, orsix optical columns if the optical columns are equally spaced apart, butdo not expose overlapping areas of the substrate. This ability to reducethe number of optical columns required to achieve a given throughput isa significant additional result to the reduction in scan distanceachieved as described above.

It will be appreciated that in an arrangement, such as that illustratedin FIG. 18, the groups of optical columns can be spaced apart with apitch equal to L/N, where L is the length of the substrate to be exposedand N is the number of optical column groups. In contrast, in anarrangement such as that illustrated in FIG. 19, the group of opticalcolumns are spaced apart with a pitch of (L+l)/N.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents. It is to be appreciated that only the Detailed Descriptionsection is intended to be used to interpret the appended claims, and notthe Summary and Abstract sections of this document.

1. A system for manufacturing a device, comprising: means for patterningeach of a plurality of beams using arrays of individually controllableelements; means for projecting the patterned beams onto a substrate; andmeans for displacing the substrate relative to the patterned beams, suchthat the patterned beams are scanned across the substrate in apredetermined scanning direction; and means for directing the patternedbeams towards the substrate using an array of lenses arranged such thateach lens directs a respective part of a respective patterned beamtowards a respective target area on the substrate, means for arrangingthe projecting means in groups, such that each of the lenses in thearrays of lenses of different ones of the projecting means groups directparts of different ones of the patterned beams to different areas of thesubstrate that are aligned in the scanning direction; and means forspacing the projecting means groups apart in the scanning direction,such that each of the projecting means groups scans the patterned beamsacross the areas of the substrate as the substrate and the projectionsystems are displaced relative to each other, the respective areasscanned by the patterned beams from the projecting means groups that areadjacent to each other in the scanning direction are contiguous.
 2. Thesystem of claim 1, further comprising means for making the contiguousareas substantially rectangular.
 3. The system of claim 2, furthercomprising: means for distributing N of the projecting means groups inthe scanning direction with a pitch of L/N, where L is a length of thesubstrate.
 4. The system of claim 1, further comprising: means forspacing two of the projecting means groups apart in the scanningdirection with a pitch of half of a length of the substrate; and meansfor displacing the substrate relative to the projecting means groups,such that one half of the substrate is displaced across a full width ofone of the projecting means groups and the other half of the substrateis displaced across the full width of the other the projecting meansgroups.
 5. The system of claim 4, further comprising: means for usingtwo arrays of projecting means in each of the groups, the two arrays ofprojecting means of each the groups exposing a respective half of thesubstrate and each of the two arrays of the projecting means exposingalternate pixel areas in the scanning direction of the respective partof the substrate.
 6. The system of claim 1, further comprising: meansfor spacing three of the groups of the projecting means apart in thescanning direction with a pitch of one third of a length of thesubstrate; and means for displacing the substrate relative to thegroups, such that a respective one third of the substrate is displacedacross a full width of each group.
 7. The system of claim 1, wherein:each of the contiguous areas has a generally rectangular main portionand at least one end portion extending in the scanning direction fromthe main portion, the at least one end portion of each of the contiguousareas having a saw-toothed shape with teeth of one of the at least oneend portion overlapping teeth of the contiguous areas.
 8. The system ofclaim 7, wherein each of the at least one end portion has a length inthe scanning direction equal to a length in the scanning direction ofeach of the groups of the projecting means.
 9. The system of claim 8,further comprising: means for distributing N of the groups of theprojecting means in the scanning direction with a pitch of (L+l)/N,where in L is a length of the substrate and l is the length in thescanning direction of each of the groups of the projecting means. 10.The system of claim 1, further comprising: means for displacing thesubstrate; and means for making the projecting means stationary.
 11. Thesystem of claim 1, further comprising: means for projecting spots of thepatterned beams using each of the arrays of lenses to expose respectiveones of the contiguous tracks on the surface of the substrate.
 12. Anapparatus comprising: an array of individually controllable elementsthat pattern a plurality of beams of radiation; a plurality ofprojection systems that project respective ones of the patterned beamsonto a substrate, each including an array of lenses arranged so thateach lens directs a part of the respective patterned beams towards arespective target area on the substrate; and a displacement system thatcauses relative displacement between the substrate and the projectionsystems, such that the respective patterned beams are scanned across thesubstrate in a predetermined scanning direction, wherein the projectionsystems are arranged in groups, such that lenses in the array of lensesof different groups direct parts of different ones of the patternedbeams to different one of the respective target areas of the substratethat are aligned in the scanning direction, wherein the groups arespaced apart in the scanning direction, such that each group scans therespective ones of the patterned beams across a respective area of thesubstrate as the substrate and the projection systems are displacedrelative to each other, and wherein the respective areas being scannedby the respective ones that are adjacent to each other in the scanningdirection are contiguous.